1. Field of the Invention
The present invention relates to a display device and in particular to a display device including a nonplanar display face on the side of an observer such as a recessed, protruding or curved face instead of a planar display face.
2. Description of the Related Art
In recent years, display devices have been used in a variety of devices as means for displaying information to an observer. Current representative display devices have employed, in their main sections, new display elements using a liquid crystal display, a plasma display, an Electroluminescence (EL) display, a Field Emission Display (FED) or the like instead of a cathode-ray tube as a mainstay in the related art. These new display elements employ a display face which is typically planar (flat) and which includes a plurality of pixels as a basic unit for forming an image arranged thereon in a matrix shape. The display elements may be provided in a reduced thickness. These new display elements are generally called flat panel displays.
The plurality of pixels arranged in a matrix shape on the planar display face of these new display elements have the same dimensions. This produces no distortions in an image on the display face and thus provides an excellent display quality unlike on the related art cathode-ray tube that forms an image through scanning by electronic beams.
In contrast, some display devices prefer a nonplanar display face such as a recessed, protruding or curved face rather than a planar display face from the viewpoint of design requirements.
Other display devices prefer a nonplanar display face such as a recessed, protruding or curved face in accordance with the direction of a plurality of observers expected, in order to provide distortion-free, visible images to respective observers watching the display face from different directions.
Display devices that must address such requirements include display devices for advertisement, display devices for ornaments, display devices for amusement, vehicle-mounted display devices, and display devices for aircraft.
JP-A-06-262964 (FIG. 1) discloses a display device of the projector type including an optical lens system projecting an image on a curved screen as a method for providing a display device including a nonplanar display face.
JP-A-10-260398 (FIG. 6) discloses a display device including a curved display face obtained by bending a liquid crystal element composed of a flexible substrate.
JP-A-2002-104024 (FIG. 3) discloses a method for inputting image data to be projected to a display element with the image data to be projected distorted by an image controller in a direction opposite to a curved screen in order to correct distortions in an image displayed on the curved screen and thus reducing the distortions in the image displayed on the curved screen.
JP-A-2002-358032 (FIG. 3) and JP-A-2000-250432 (FIGS. 5, 6, 7, 8, 10) disclose a display device including an optical element composed of an optical fiber plate arranged in front of a planar display element with the display face on the observer's side made into a curved shape instead of using a projector.
With the display device of the projector type disclosed in JP-A-06-262964, a three-dimensional appearance is given to an image displayed on the curved screen although the image is distorted. The projector system has problems such as a large depth (thickness) of the display device and the optical system vulnerable to vibrations. The image is blurred unless the curved screen is positioned at the focal point of the optical lens. Thus, the shape of the nonplanar screen is limited.
The display device disclosed in JP-A-10-260398 provides a curved display face by bending a flexible substrate constituting a liquid crystal display panel. This arrangement is simple but the material, thickness and heat resistance of the flexible substrate are limited. It is currently difficult to manufacture a liquid crystal display panel of the active matrix type made of a thin-film transistor or the like that offers high picture quality. The nonplanar display face has the shape of a simple curved face and the shapes of a nonplanar display face that may be manufactured are limited.
With the display device of the projector type disclosed in JP-A-2002-104024, image data is corrected by the image controller and is inputted to the display element and this arrangement is applicable to correction of distortions in an image presented on various types of nonplanar display devices. A plurality of pixels arranged in a matrix shape constituting the display face of a display element to which image data is to be inputted have the same dimensions and distortions in an image is corrected assuming a certain dimension of a pixel of the display element as the minimum unit. Depending on the shape of a particular nonplanar display face, uncorrectable distortions in an image are conspicuous.
With the display devices disclosed in JP-A-2002-358032 and JP-A-2000-250432, an image on the planar display element is enlarged or reduced or a nonplanar display face is provided in an simple way by using an optical element composed of an optical fiber plate. However, JP-A-2002-358032 and JP-A-2000-250432 do not refer to the problem of distortions in an image on a nonplanar display face or means to solve the problem.